This invention relates to a method and apparatus for forming fiber mixtures from a plurality of fiber types by sequentially taking, from different fiber lots such as fiber bales, partial quantities which are small with respect to the entire quantity of the mixture.
German Laid-Open Applications (Offenlegungsschriften) Nos. 1,685,596 (to which corresponds U.S. Pat. No. 3,577,599) and 2,063,415 disclose a method according to which a plurality of fiber bales containing the same kind of fiber are positioned next to a plurality of fiber bales of another type of fiber. A carriage is moved past the fiber bales and the bale opener mounted thereon takes from each fiber type a partial quantity so that the composition of the partial quantities obtained during each pass has the desired predetermined mixture ratio. At the same time, care is taken that, in case the required individual partial quantity of one fiber type is not reached during the opening operation of one pass, the carriage does not move on to the subsequent fiber type, but is ordered to return for making up the deficiency. Although such a method is adapted for obtaining a mixture of predetermined proportions of fiber types wherein the individual proportions are in each instance taken from a plurality of fiber bales, several disadvantages are involved with this method. The individual fiber bales even of the same fiber type have fluctuating dimensions, compressions and weights. According to the method, such an amount of fiber material is removed each time from a plurality of fiber bales of one fiber type until a quantity corresponding to the intended proportion is reached. Thus, during each pass of the carriage (on which the opener is mounted), from a plurality of fiber bales of one fiber type a predetermined quantity has to be removed or has to be complemented, while the quantities remaining in the fiber bales are not taken into account at all. As a result, it is unavoidable that in the individual fiber bales eventually residual fibers remain which disturb to a substantial extent the rhythm of operation, since they have to be processed separately, thus requiring undesirable additional labor and expense. It is a further disadvantage that a partial quantity is always taken from a plurality of fiber bales, so that the mixture can be obtained only in steps and therefore it cannot be optimally homogeneous.